The present invention relates to electrical systems which comprise electrical loads, various stored energy sources, and one or more electrical energy supplying means such as a generator. More specifically, the present invention focuses on a system and method which may be utilized in electrical networks, such as a vehicle electrical system, where the stored energy sources are controllably configured in such a manner as to facilitate the transfer of maximum available electrical energy in the electrical network to the associated electrical loads in order to satisfy the operating condition requirements. Additionally, the device is configured to controllably transfer electrical energy from a first electrical energy source to one or more electrical energy sources and their respective electrical loads in the electrical system corresponding to the operating condition and in such a way as to avoid overloading or otherwise detrimentally affecting said first electrical energy source.
Electrical systems are typically comprised of a generator, electrical loads, and a stored energy source. The stored energy sources function during the time when the generator is not operating, so as to provide the required electrical energy to the electrical loads. For example in a vehicle electrical system an operating condition may require a generator, which transforms mechanical energy into electrical energy, to supply electrical energy when the vehicle engine is operating, and one or more stored energy sources, such as a battery, to supply electrical energy during the periods when the vehicle engine is not operating. Another example is where a hybrid vehicle operating condition may require its on-board generator to recharge its depleted batteries in addition to providing electrical energy to various electrical devices while the vehicle mechanical engine is operating, and its batteries to provide electrical energy during the periods when the vehicle's mechanical engine is turned off and the vehicle electrical engine is employed to propel and operate the vehicle.
Such traditional electrical systems ordinarily comprise a main and an auxiliary system of stored energy sources. Both the main and auxiliary systems may further be comprised of a series of stored energy sources. For instance, in certain vehicles, the electrical system is configured such that there is a main stored energy source which supplies electrical energy to main electrical loads during engine startup and whenever the generator is not operating but there is an auxiliary stored energy source which provides electrical energy to the auxiliary electrical loads. The main and auxiliary systems are connected to the electrical system in a parallel configuration and may contain switchable means to provide isolation or interconnection of any source of electrical energy to the respective electrical loads.
In such electrical systems the main and auxiliary systems are electrically isolated from each other in a unidirectional manner, meaning that the flow of electrical energy can only take place in a pre-designated direction, for example from the main system to the auxiliary system or vise versa. This is done so a single generator may recharge main and auxiliary batteries simultaneously, but the batteries are unable to discharge into each other. Ordinarily, this is accomplished by incorporating an isolation diode between the generator and each stored energy source.
A common design of vehicle electrical systems is such that the main battery system provides electrical energy to the engine starter to start the engine, and the auxiliary system provides electrical energy to the electrical loads while the vehicle's engine is not operating. In the event that the main system is depleted or otherwise defective, the auxiliary system is incapable of transferring energy to the main system to enable engine cranking unless a manual switch or relay is provided. Similarly, if the auxiliary system has exhausted its energy and there still remains a critical need to provide electrical energy to the electrical loads, the main system is incapable of transferring its energy to the auxiliary system unless a manual switch or relay is provided. Either case of manual switching requires consideration of the circuit effect when inserting a high energy source into an electric circuit that contains a very low source impedance inherent to a discharged battery or a possible short circuit that may have caused battery discharge. This generally leads to a switching means that disconnects or isolates the depleted stored energy source that is being replaced by the one with the higher energy. This still does not adequately address the case of a short circuit that may have caused the initial battery discharge.
Although various systems have been proposed which touch upon some aspects of the above problems, they do not provide solutions to the existing limitations in electrical energy transfer between systems of stored energy sources, generators, and loads. For example, Renehan, U.S. Pat. No. 6,215,277 discloses an electrical charging system which is capable of charging two sets of stored energy sources at different voltages, but does not address bi-directional electrical energy transfer between these sources which is the subject of the present invention. In Lambert, U.S. Pat. No. 5,162,720, the concept of the invention is to provide means for connecting the engine battery, the auxiliary battery, and the supplemental electric current source, and for permitting unidirectional current flow to the engine battery from the supplemental electric current source while the vehicle engine is not operating. The present invention does not require an operational distinction between auxiliary battery and engine battery, and furthermore, the flow of electrical energy from the stored energy sources may occur in either direction. The Hoinsky patent, U.S. Pat. No. 4,090,122 discloses a vehicle electrical system which includes a high capacity storage battery in addition to the standard vehicle battery to be utilized during periods when the vehicle is at rest, but it does not address electrical energy management between such stored energy sources. Consequently, there is a need for an electrical energy source controller that controllably permits electrical isolation between stored energy sources in an electrical system while allowing bidirectional energy transfer between them. Furthermore, the present invention is capable of transferring the maximum electrical energy in the electrical system to the stored energy sources and their associated electrical loads in response to the vehicle operating condition.
In modern vehicle designs an electrical energy source may take on various forms. Mechanical, chemical, and solar energy, among others, may be converted into electrical energy for consumption by vehicle electrical loads. For instance, in a motor vehicle, an electrical energy source usually takes on the form of a generator where mechanical energy is converted into electrical energy. The electrical energy source of a solar-powered vehicle, for example, converts solar energy into electrical energy. Additionally, the electrical energy source is also responsible to provide and maintain the necessary electrical energy in the other electrical energy sources in the system. The first task, i.e. providing electrical energy to the electrical loads, is ordinarily more critical than the second. Modem vehicles rely heavily on their on-board electrical devices. Any disruption in the transfer of energy to such devices may lead to an inoperable vehicle. For instance, a computer-controlled fuel injection system must be operational for the engine to continue operating. A first electrical energy source providing electrical energy to such loads must not be overloaded or otherwise detrimentally affected by the demand of electrical energy from other electrical energy sources or low priority loads. The other electrical energy sources must be disconnected if they become a source of overload for said first electrical energy source. Furthermore, it is desirable to monitor said first electrical energy source such as a generator and extract electrical energy from it whenever it is possible to do so without causing an overload. Therefore, there is a need for an electrical energy source controller which monitors electrical energy sources in a vehicle electrical system and controllably extracts electrical energy from a first electrical energy source to one or more electrical energy sources and their associated electrical loads based on an operating condition requirement.